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In order to improve the mechanical properties and corrosion resistance of 2A97 aluminum-lithium alloy, this research develops a novel strain heat-treatment technology. Surprisingly, 2A97 alloy treated by 4% pre-strain and 48 h deep cryogenic aging exhibits excellent mechanical properties, whose yield strength, tensile strength, and elongation are 573.7 MPa, 593.6 MPa, and 14.25%, respectively. Furthermore, the corrosion resistance of samples treated by the above pre-strain deep cryogenic aging process is two times as much as traditional T6 aged. This study deeply investigates the influence of various precipitates in 2A97 alloy on its performance through microstructure analysis. The results show that the introduction of pre-strain inhibits the precipitates of the T1 and δ′ phases at the grain boundaries, and prevents the formation and widening of precipitate-free zones. At the same time, it reduces the potential difference between grain boundaries and matrix, and enhances the corrosion resistance of 2A97 alloy. Deep cryogenic can inhibit recovery and maintain deformation dislocation, so that a large number of defects produced by pre-strain promote the nucleation and diffusion of precipitates in the matrix, resulting in tiny and uniformly distributed precipitates. Therefore, the novel pre-strain deep cryogenic aging not only endues 2A97 alloy excellent performance, but also offers a new strategy for controlling precipitation.

Abstract Iron-based nanotubes are promising candidates for high performance electromagnetic wave absorbing fillers due to their high aspect ratio, light weight, high axial permeability and high saturation magnetization. Furthermore, the introduction of carbon can improve dielectric loss and block the agglomeration of iron nanotubes. Here, Fe@C composite nanotubes were prepared by introducing carbon onto the surface of precursor α-FeOOH’ fibers followed by hydrogen-thermal annealing. We find that Fe@C composite nanotubes retain the one-dimensional nanostructure of the precursor throughout the annealing. The well-developed lattice and nanostructure of Fe@C nanotubes endow high saturation magnetization, high anisotropy, suppressed eddy current effect and cross-particle exchange coupling as well, and thus contribute to an enhanced permeability. Coatings with Fe@C as fillers achieve a reflection loss of up to −69.34 dB at 3.37 GHz at the matching thickness of 3.97 mm. The Fe@C composite nanotubes developed here are a promising candidate for high performance electromagnetic wave absorbing fillers.

FeSiAl alloys with a composition of Fe-9.6Si-5.4Al, also known as Sendust alloys, present the unique potential to exhibit efficient electromagnetic wave absorption (EMA) in the P-band. However, the electromagnetic properties of this type of alloy are highly sensitive to the shape, microstructure, and microchemistry, which then inspire the current research. The evolution of the microstructure/microchemistry of FeSiAl particles was systematically revealed in a single particle scale for the first time, and the resulting influence on the electromagnetic properties was investigated. Recrystallization occurs in the annealing process on FeSiAl particles and the oxide films on the surface evolve evidently when annealed in 5%H2/Ar or air, which can conduce improved electromagnetic properties. The FeSiAl particles annealed in 5%H2/Ar present efficient EMA in the P-L band while those in air contribute to high reflection loss. This work indicates the feasibility of achieving a high and adjustable EMA efficiency in the P-L band through microstructure and microchemistry tailoring.

The macro-galvanic effect in friction stir welding (FSW) joints is contributive for accelerating the localized corrosion of 7xxx aluminum alloy weldment. A process route, solid solution treating→FSW→T76 ageing (SSW-T76), was developed to weak the macro-galvanic effect. The microstructure and corrosion of joints prepared from SSW-T76 route and the conventional route (T76→FSW, T76W) were comparatively investigated. It was found that both precipitate coarsening and solute segregation were effectively suppressed when the route was changed from T76W to SSW-T76. The discrepancy in microstructure, micochemistry and corrosion potential between the base material (BM), the heat-affected zone (HAZ) and the nugget zone (NZ) was narrowed, leading to suppressed macro-galvanic effect and thereafter to decreased pitting and IGC.

A high-strength and anti-intergranular corrosion (IGC) Al-6.8Zn-2.2 Mg-Sc-Zr alloy (AS alloy) was designed, and the effects of Sc addition and Cu removal on the microstructure, mechanical properties and corrosion behavior were systematically investigated. Based on transmission electron microscopy (TEM) and Kelvin probe force microscopy (KPFM) techniques, the underlying causes of IGC and exfoliation corrosion (EXCO) of the AS alloy were investigated, and the corrosion mechanism of AS alloy was finally obtained. The AS alloy exhibits excellent mechanical properties with a tensile strength of 601 MPa in the peak-ageing condition at 120 °C, which comes from the pinning effect of Al3(Sc, Zr) dispersions. Moreover, AS alloys of T6 and T74 conditions show outstanding IGC and EXCO resistance. On the one hand, the fine, near-ellipsoidal grains in AS alloy alleviate the peeling stress caused by IGC products by blocking the formation of wedge-shaped gaps along GBs, which then bring about improved EXCO resistance. On the other hand, the removal of Cu from the traditional Al-Zn-Mg-Cu alloy avoids the segregation of Cu into GBs and thereafter reduces the fluctuations of the potential and the electron work function (EWF) across the GBs; the addition of Sc induces the high fraction of LAGBs and thus weakens the solutes' segregation at GBs, which can be beneficial for smoothing the fluctuation of corrosion potential (Ecorr) to enhance the IGC resistance.

An Al–Zn–Mg-Sc-Zr alloy with high Zn was prepared to obtain ultra-high strength in the present study. The microstructure of the aged samples and the friction stir welding (FSW) joints were investigated by optical microscopy, electron backscatter diffraction and transmission electron microscopy. The mechanical properties were evaluated by microhardness and tensile tests. Results show that the peak microhardness of the aged Al–Zn–Mg-Sc-Zr alloy was ∼212.2 Hv. Strengths up to 697.2 MPa in the yield strength and 721.8 MPa in the ultimate tensile strength were obtained after ageing at 120 °C for 24 h, and the elongation was ∼9%. The ultra-high strength was mainly attributed to the precipitate strengthening from η′ and Al3ScxZr1-x precipitates, solid solution strengthening and fine grain strengthening. Soft regions with hardness of ∼122 Hv were developed near the interfaces between heat-affected zone and thermo-mechanically affected zone due to the coarsening and/or dissolution of strengthening precipitates. The joint coefficient was ∼69.5% for the Al–Zn–Mg-Sc-Zr alloy. Fine recrystallized grains with an average diameter of ∼1.8 μm were formed in the nugget zone (NZ), and these newly formed fine grains experienced further deformation and resulted in high fractions of substructure and deformed grain. The size and shape of Al3ScxZr1-x precipitates remain almost unchanged during ageing at 120 °C and the FSW processing. The existence of η phase in the NZ was associated with the Al3ScxZr1-x particles, indicating the heterogeneous precipitation of η precipitates on the Al3ScxZr1-x precipitates during FSW.

The alkali mercerizing process of semicrystalline cotton fiber (CF) is widely used in the printing and dyeing industry. The crystallinity change in the mercerizing process has been studied and certain laws have been obtained, but there is still a certain distance between the theoretical research results and the practical applications. CF is almost composed of cellulose, combined with the photoluminescence (PL) phenomenon of cellulose; herein, the varying crystallinity is correlated with its PL behavior after being treated with different concentrations of NaOH. In line with the characteristics of nonconventional luminogens, CF enjoys excitation-dependent emission and persistent room temperature phosphorescence (p-RTP) behavior. The emission spectra of all samples under the same excitation wavelength indicate that the change of CF crystallinity has a significant impact on its fluorescence and p-RTP emission. As the concentration of NaOH increases, the varying trend of quantum efficiency (QY) is consistent with the changed crystallinity of CF. Interestingly, the lifetime of p-RTP is exactly the opposite of the crystallinity change law. Clustering-triggered emission (CTE), crystallization-Induced Phosphorescence (CIP) mechanism, and the swelling due to hydrated sodium ions can reasonably explain these interesting photophysical processes, which also can be supported by theoretical calculations. The above studies have basically clarified the inherent law between the crystalline change of CF and the PL emission behavior during the alkali treatment process, which can be used as a theoretical reference for real-time monitoring of CF crystallinity changes using the spectral method in the actual cotton mercerizing process.

Anisotropic mechanical behavior of the Ti-6Al-4V alloy is essential for its forming and service. Generally, it is preferable to minimize the in-plane anisotropy of Ti-6Al-4V sheet. The present work investigates the anisotropy of Ti-6Al-4V alloy by tensile tests along the rolling direction (RD), transverse direction (TD), and diagonal direction (DD) of the sheet, evaluating the anisotropic yield and flow behaviors and exploring the causes of these anisotropic properties. The intrinsic deformation mechanism of Ti-6Al-4V alloy tensioned along different directions was studied with Schmid factor and kernel average misorientation (KAM) analysis. The samples tensioned along the RD and TD of the sheet (denoted as RD sample and TD sample) show similar yield stress, while tensile along the DD (denoted as DD sample) leads to lower yield strength. The mechanical anisotropy exhibited by the Ti-6Al-4V sheet is closely related to the crystallographic texture. The flow stresses of the RD and TD samples are higher than that of the DD sample due to the higher density of dislocations generated during the tensile deformation, in which prismatic ⟨a⟩ dislocations make a great contribution to coordinating plastic deformation.

The quench-induced precipitation and subsequent aging response in 2A97 aluminum alloy was investigated based on the systematic microstructure characterization. Specifically, the influence on precipitation from grain structure was examined. The results indicated the evident influence from the cooling rate of the quenching process. Precipitation of T1 and δ′ phase can hardly occur in the specimen exposed to water quenching while become noticeable in the case of air cooling. The yield strength of 2A97-T6 alloy de-graded by 234 MPa along with a comparable elongation when water quenching was replaced by air cooling. Sub-grains exhibited a much higher sensitivity to the precipitation during quenching. The presence of dislocations in sub-grains promoted the quench-induced precipitation by acting as nucleation sites and enhancing the diffusion of the solute. A quenching rate of 3 °C/s is tolerable for recrystallized grains in 2A97 Al alloy but is inadequate for sub-grains to inhibit precipitation. The study fosters the feasibility of alleviating quench-induced precipitation through cultivating the recrystallization structure in highly alloyed Al–Cu–Li alloys.

This study developed a versatile and facile method for creating pores and tuning the porous structure in the polymer latex films by selectively etching the added functional polyvinyl pyrrolidone (PVP) molecules. The pore formed in the latex films had a similar morphology to that of PVP aggregation before etching. This observation promotes us to regulate the pore morphology that determines the film’s property, such as air permeability through varying the PVP molecule weight and dosage. To this end, the effects of PVP molecule weight and dosage on the pore formation were systematically studied. The results showed that the average pore size of porous film decreased from >10 μm to sub-micron (about 0.4 μm) as the molecular weight or the dosage of PVP increased. This was ascribed to the strong adsorption affinity of PVP molecule onto the latex particle surface, which further hindered the diffusion and self-assembly of PVP molecule. In addition, this interaction became much stronger when the higher molecule weight of PVP or the higher dosage of PVP was employed, leading to the decreased size of PVP aggregation, as well as the formed pores in the latex films. Furthermore, the addition of PVP had little effect on the color of coated fabric based on the results of CIE L*a*b* measurement. The proposed facile method can be used to improve the air permeability of coated fabrics.

Herein, graphite/Fe3O4/resin-based composite absorbers are prepared by selective laser sintering (SLS) and vacuum impregnation of epoxy resin. The effects of different graphite-Fe3O4 powder compositions on the absorbing and mechanical properties of the composites are investigated. The results show that with the increase of Fe3O4 content, the absorption performance of the composites first increases and then decreases, and the absorption peak gradually moves from high frequency (12-18 GHz) to low frequency (2-8 GHz). The bending strength of composites decreases with the increasing of Fe3O4 content. When the mass ratio of graphite-Fe3O4 is 4:3, the wave absorption performance is the best, the minimum reflection loss is -54.8 dB, the effective absorption bandwidth is 2.8 GHz (8.72-11.52 GHz), and the bending strength is 11 MPa, which is 9 times higher than that of SLS plain billets. This is because the increase of the Fe3O4 content in the hybrid powder increases the number of heterogeneous interfaces, but decreases the number of holes inside the composite, which affects the number of microwave reflections inside the material, resulting in different wave absorption and mechanical properties. The graphite/ferrite/resin matrix composites prepared by SLS technology achieve the synergy of lightweight, high strength, and good wave absorption properties. [ABSTRACT FROM AUTHOR]